KR20110138195A - Alkali-containing monolayer graphene and electric device comprising same - Google Patents

Abstract

PURPOSE: An alkali metal containing monolayer graphene and an electronic device including the same are provided to maintain the inherent characteristic of the graphene by forming high band gap in the graphene through the localization of charges based on non-chemical bonds. CONSTITUTION: Alkali metals are prepared by being selected from lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metals are placed on at least one surface of a monolayer graphene. The alkali metals are in second dimensional thin film structure. About 30-99% of the entire surface area of the monolayer graphene is occupied by the alkali metals. The band gap of the monolayer graphene is more than or equal to 0.4eV. The area of the monolayer graphene is more than or equal to 1cm^2.

Description

Monolayer graphene comprising alkali metal, and electronic device comprising the same

The present invention relates to an alkali metal-containing single layer graphene and an electric device including the same, and may be usefully used in various electric devices including a transistor by incorporating an alkali metal into a single layer graphene and semiconductorizing the semiconductor.

In general, graphite (graphite) is a structure in which two-dimensional graphene of plate-shaped carbon atoms are connected in a hexagonal shape. Recently, one or more layers of graphene were stripped from graphite, and the characteristics of the graphene were examined to find very useful properties different from the existing materials.

Graphene, for example, has a metallicity of its own and thus becomes conductive. This conductivity prevents the graphene from having a band gap as shown in FIG. 1. Therefore, in order to impart semiconductor characteristics to graphene, it is necessary to form a band gap.

An object of the present invention is to provide a graphene imparted with semiconductor characteristics.

Another object of the present invention is to provide an electric device having graphene imparted with the semiconductor properties.

According to the sun,

A single layer graphene containing alkali metal is provided.

According to one embodiment, the alkali metal is at least one selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr).

According to one embodiment, sodium (Na) may be used as the alkali metal.

According to one embodiment, the alkali metal may be present on at least one surface of the single layer graphene.

According to one embodiment, the alkali metal may have a two-dimensional thin film structure.

According to one embodiment, the alkali metal may have the form of a thin film, nanorods and / or nanoclusters.

According to one embodiment, the alkali metal may comprise about 30 to about 99% of the total surface area of the single layer graphene.

According to one embodiment, the alkali metal may comprise about 50 to about 90% of the total surface area of the single layer graphene.

According to one embodiment, the single layer graphene may have a bandgap of about 0.4 eV or more.

According to one embodiment, the single layer graphene may have a bandgap of about 0.45 eV to about 0.8 eV.

According to one embodiment, the single layer graphene may have a bandgap of about 0.6 eV to about 0.8 eV.

According to one embodiment, the single layer graphene may have an area of 1 cm ² or more.

According to one embodiment, the single layer graphene may have 10 or less wrinkles per unit area of 1000 μm ² .

According to one embodiment, the single layer graphene may be present in a range of 99% or more per 1 mm ² unit area.

According to one embodiment, the substrate may be further provided under the single layer graphene.

According to one embodiment, the substrate may be an inorganic substrate such as a Si substrate, a glass substrate, a GaN substrate, a silica substrate; Metal substrates such as Ni, Co, Fe, Pt, Pd, Au, Al, Cr, Cu, Mn, Mo, Rh, Ir, Ta, Ti, W, U, V and Zr; The board | substrate which consists of one or more of plastic substrates; is mentioned, for example.

According to another sun

An electric device having a single layer graphene containing the alkali metal is provided.

Examples of the electric element include a sensor, a bipolar junction transistor, a field effect transistor, a heterojunction bipolar transistor, a single electron transistor, a light emitting diode, an organic light emitting diode, and the like.

Since the alkali-containing single layer graphene forms a high band gap through the localization of charges by non-chemical bonding to semiconductor the graphene, it becomes possible to maintain the inherent characteristics of the graphene itself. Therefore, it is possible to apply a high band gap while maintaining the characteristics such as high mobility of the graphene, it can be usefully used in various electrical devices such as transistors.

1 shows a band gap of a typical graphene.
2 is a schematic diagram illustrating a structure of a field effect transistor according to one embodiment.
3 shows the light transmittance of the graphene monolayer obtained in Preparation Example 1. FIG.
4 to 7 show a sodium deposition process of the single layer graphene obtained in Example 1.
8 shows the bandgap measurement results of the sodium-containing monolayer graphene obtained in Example 1. FIG.

According to one aspect, a single layer graphene containing alkali metal is provided.

The term "graphene" as used herein refers to a plurality of carbon atoms covalently linked to each other to form a polycyclic aromatic molecule, wherein the carbon atoms linked to the covalent bond form a six-membered ring as a basic repeating unit, It is also possible to further include a 5-membered ring and / or a 7-membered ring. As a result, the graphene monolayer appears as a single layer of covalently bonded carbon atoms (usually sp ² bonds), and may have a thickness of substantially one carbon atom layer. The graphene monolayer generally has a light transmittance of about 97 to about 98%.

As shown in FIG. 1, when an alkali metal is contained on a single layer graphene that exhibits conductivity because there is no band gap, a band gap may be formed, and the single layer graphene may exhibit semiconductor characteristics. In other words, the alkali metal may cause charge separation of the single layer graphene through non-chemical bonding such as adsorption on at least one surface of the single layer graphene to form a band gap.

This bandgap is formed by non-chemical bonds, for example, by physical bonds such as adsorption, rather than chemical bonds, so that the net charge of the graphene itself becomes "zero." Therefore, when the band gap is applied to the graphene in this manner, since the band gap is formed only through the localization of the charge, the graphene itself is not damaged, thereby reducing the high mobility of the graphene itself. Without the band gap to the single layer graphene can be semiconductorized.

As the size of the bandgap increases, I _on / I _off increases, so that it is possible to improve the characteristics of the electric element employing the band gap. The band gap formed on the single layer graphene may be about 0.4 eV or more, for example, about 0.45 eV to about 0.8 eV, about 0.6 eV to about 0.8 eV.

Such a band gap can be adjusted according to the type and concentration of alkali metal, and the alkali metal may be lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium ( One or more selected from the group consisting of Fr) can be used, for example sodium (Na) can be used.

Such alkali metal is present on at least one surface of the single layer graphene, and forms non-chemical bonds such as adsorption through methods such as atomic layer deposition (ALD) and chemical vapor deposition (CVD). Through such bonding, the alkali metal forms an alkali metal nanostructure on the single layer graphene, and the nanostructure may have a two-dimensional structure such as a thin film.

The nanostructures formed by the alkali metal on the single layer graphene may be present in various forms such as nanodots, nanoribbons, nanocavities, nanorods, nanoclusters, and nano islands as two-dimensional thin films. For example, it may be formed to a thickness of about 1 layer to about 100 layers, or may be formed to a thickness of about 2.0 to about 200Å. The region in which these alkali metals are present may occupy about 30% to about 99%, for example about 50% to about 90% of the total surface area of the monolayer graphene.

As the two-dimensional nanostructure of the alkali metal as described above forms a non-chemical bond on at least one surface of the single-layer graphene, localization of the charge occurs to form a band gap of the graphene as shown in FIG. 2. Since the band gap is formed without damaging the graphene itself, the graphene semiconductor is achieved while maintaining inherent physical properties such as high mobility of the graphene.

As described above, the single layer graphene containing the alkali metal may further include a substrate thereunder. There is no restriction | limiting in the kind as such a board | substrate, For example, Inorganic substrates, such as a Si substrate, a glass substrate, a GaN substrate, a silica substrate; Ni, Co, Fe, Pt, Pd, Au, Al, Cr, Cu, Mn, Mo, Rh, Ir, Ta, Ti, W, U, V, and Zr substrates; One or more metal substrates made of any one of plastic substrates can be used.

The alkali metal may be formed on a single layer graphene by various deposition processes, for example, by atomic layer deposition, chemical vapor deposition, sputtering, evaporation, or the like.

The graphene on which the alkali metal is formed uses a single layer graphene, and when the alkali metal is formed to an atomic layer thickness on the single layer graphene, a band gap is formed to impart semiconductor properties to the graphene. . In this case, the single layer graphene used may be manufactured by various methods, and the following method may be exemplified, but is not limited thereto.

-Graphene Formation Process (Weather Method)

As a method of forming graphene on the graphitized catalyst metal film, a gas phase method or a liquid phase method can be used, and any method known in the art can be used without limitation.

For example, the gas phase method is formed by forming a graphitization catalyst in the form of a film, heat treatment while adding a gaseous carbon source thereto, thereby producing graphene, and then growing it under cooling. That is, when the graphitization catalyst is heat-treated at a predetermined temperature for a predetermined time while supplying a gaseous carbon source at a predetermined pressure in a chamber in the form of a membrane, the carbon components present in the gaseous carbon source are bonded to each other to form a hexagonal plate. Graphene is produced while forming a structure, and cooling the graphene at a predetermined cooling rate allows a graphene sheet having a uniform arrangement to be obtained on the graphitized catalyst metal film.

Carbon may be supplied as a carbon source in the graphene sheet forming process, and any material that may exist in the gas phase at a temperature of 300 ° C. or higher may be used without particular limitation. The gaseous carbon source may be a compound containing carbon, preferably a compound having 6 or less carbon atoms, more preferably a compound having 4 or less carbon atoms, and more preferably a compound having 2 or less carbon atoms. As such an example, one or more selected from the group consisting of carbon monoxide, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene and toluene can be used.

Such a carbon source is preferably introduced at a constant pressure in a chamber in which the graphitization catalyst is present, and in the chamber, only the carbon source may be present, or may be present together with an inert gas such as helium, argon, or the like.

Hydrogen may also be used in addition to the gaseous carbon source. Hydrogen can be used to control the gas phase reaction by keeping the surface of the metal catalyst clean, and can be used 5 to 40% by volume of the total volume of the vessel, preferably 10 to 30% by volume, more preferably 15 to 25 Volume%.

Graphene is formed on the surface of the graphitization catalyst by introducing the gaseous carbon source into a chamber in which the graphitization catalyst in the form of a film is present and then heat-treating it at a predetermined temperature. The heat treatment temperature acts as an important factor in the production of graphene, for example, may be used 300 to 2000 ℃, or 500 to 1500 ℃.

As described above, the heat treatment may be performed to maintain the graphene for a predetermined time at a predetermined temperature. That is, since the graphene is generated when the heat treatment process is maintained for a long time, the resulting graphene thickness can be increased. If the heat treatment process is shorter, the resulting graphene thickness is reduced. Therefore, in addition to the type and supply pressure of the carbon source, the type of graphitization catalyst, and the size of the chamber, the retention time of the heat treatment process may act as an important factor in order to obtain a desired thickness of the single layer graphene. The holding time of such a heat treatment process can be maintained for 0.001 to 1000 hours, for example.

As the heat source for the heat treatment, inducting heating, radiant heat, laser, IR, microwave, plasma, UV, surface plasmon heating and the like can be used without limitation. Such a heat source is attached to the chamber and serves to raise the inside of the chamber to a predetermined temperature.

After the heat treatment as described above, the heat treatment result is subjected to a predetermined cooling process. Such a cooling process is a process for allowing the generated graphene to grow uniformly and be uniformly arranged. As the sudden cooling may cause cracking of the generated graphene sheet, it may be gradually cooled at a constant speed as much as possible. Examples thereof include cooling at a rate of 0.1 to 10 ° C. per minute, and it is also possible to use a method such as natural cooling. The natural cooling simply removes the heat source used for the heat treatment, and it is possible to obtain a sufficient cooling rate even by removing such a heat source.

The heat treatment and cooling process as described above may be performed in one cycle, but it is also possible to repeatedly generate graphene having a dense structure.

The graphitization catalyst is used in the form of a metal film, which is a plate-like structure, and serves to help the carbon components provided from the carbon source combine with each other to form a hexagonal plate-like structure by contacting the carbon source. Examples thereof include catalysts used for graphite synthesis, carbonization induction, or carbon nanotube production. For example, one or more selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta, Ti, W, U, V and Zr can be used. have.

The graphene obtained by the gas phase method is obtained through a pure material of a gaseous phase and a high temperature heat treatment, and thus has a homogeneous structure with few defects.

Graphene Formation Process (Polymer Method)

Another method of forming the single layer graphene is a polymer method. As a step of bringing the liquid carbonaceous material into contact with the graphite catalyst metal film, a process of applying a carbon-containing polymer, which is a carbonaceous material, onto the substrate may be used.

In the case of using a carbon-containing polymer as the carbon-based material, any carbon-containing polymer may be used without limitation. However, in the case of using a self-assembled polymer, the polymer is regularly arranged in the vertical direction on the surface of the catalyst, thereby providing a more compact structure. It becomes possible to form a pen.

As the self-assembled polymer forming the self-assembled film, at least one self-assembled polymer selected from the group consisting of an amphipathic polymer, a liquid crystal polymer and a conductive polymer can be used.

Since the amphiphilic polymer has both hydrophilic and hydrophobic functional groups in the structure, the amphiphilic polymer may be arranged in a constant orientation in an aqueous solution, for example, a Langmuir-Brojet array, a dipping array, a spin array, and the like. The amphiphilic polymer may include a hydrophilic functional group including at least one selected from the group consisting of an amino group, a hydroxyl group, a carboxyl group, a sulfate group, a sulfonate group, a phosphate group, or a salt thereof; And halogen atom, C1-C30 alkyl group, C1-C30 halogenated alkyl group, C2-C30 alkenyl group, C2-C30 halogenated alkenyl group, C2-C30 alkynyl group, C2-C30 halogen ring alkynyl group, C1-C30 alkoxy group, C1- At least one selected from the group consisting of a C30 halogenated alkoxy group, a C1-C30 heteroalkyl group, a C1-C30 halogenated heteroalkyl group, a C6-C30 aryl group, a C6-C30 halogenated aryl group, a C7-C30 arylalkyl group and a C7-C30 halogenated arylalkyl group It includes a hydrophobic functional group comprising a. Such amphiphilic polymers include capric acid, lauric acid, palmitic acid, stearic acid, myristoleic acid, palmitoleic acid, oleic acid, stearic acid, linolenic acid, caprylamine, la Examples include uryl amine, stearyl amine, oleyl amine, and the like.

The liquid crystal polymer has a property of being arranged in a certain orientation in the liquid phase, and the conductive polymer has a property of forming a specific crystal structure by dissolving them in a solvent to form a film after the solvent is volatilized to form a specific crystal structure, Spin coating arrangements and the like. Examples of such polymers include polyacetylene, polypyrrole, polythiophene, polyaniline, polyfluoroene, poly (3-hexylthiophene), polynaphthalene, poly (p-phenylene sulfide), and poly ( p-phenylene vinylene) type | system | group etc. are mentioned.

The carbon-containing polymer may have at least one polymerizable functional group such as a carbon-carbon double bond or a carbon-carbon triple bond in the structure. After forming a film | membrane, these can induce superposition | polymerization between polymers by superposition | polymerization processes, such as ultraviolet irradiation. Since the carbon-based material obtained by such a process has a high molecular weight, it becomes possible to suppress volatilization of carbon during subsequent heat treatment.

Such a polymerization process of the carbon-containing polymer may be carried out before or after coating on the graphitization catalyst. That is, when the polymerization between the carbon-containing polymer is induced before coating on the graphitization catalyst, the polymer film obtained by a separate polymerization step can be transferred onto the graphitization catalyst to form a carbon-based material layer.

The carbon containing polymer may be arranged on the graphitization catalyst by various coating methods, for example, Langmuir-Blodgett, dip coating, spin coating, vacuum deposition, etc. Can be arranged in In particular, according to such an application method, the carbon-containing polymer may be applied on the substrate as a whole or selectively applied on the graphitization catalyst.

In addition, the amphiphilic organic material in the self-assembled organic material includes both hydrophilic and hydrophobic sites in the molecule, and the organic material, for example, the hydrophilic site of the polymer, binds to the hydrophilic graphite catalyst and preferentially arranges it evenly on the catalyst layer. The hydrophobic sites of the amphiphilic organics are exposed to the opposite side of the substrate to bond with other amphiphilic organics that are not bound to the catalyst layer, for example the hydrophilic sites of the amphiphilic polymer. When the content of the amphiphilic organic material is sufficient, the amphiphilic organic material is sequentially deposited on the catalyst layer by such a hydrophilic-hydrophobic bond. These are combined sequentially to form a plurality of layers, and then constitute a graphene layer by heat treatment. Therefore, by selecting the appropriate amphiphilic organic material and controlling the thickness of the organic film formed by controlling the content, it is possible to control the number of layers of graphene into a single layer, so that graphene having an appropriate thickness can be manufactured according to the purpose. Will have

-Graphene Formation Process (Liquid Method)

As another method of forming the single layer graphene, a liquid phase method may be mentioned. In such a liquid phase method, graphene may be formed by bringing a liquid carbonaceous material into contact with a graphite catalyst metal film and then performing heat treatment.

As the process of contacting the liquid carbonaceous material with the graphitized catalyst metal film, a process of preliminary heat treatment after immersing the substrate in a liquid carbonaceous material that is a carbonaceous material may be used.

Examples of such liquid carbonaceous materials include organic solvents, and any carbon solvent may be used as long as it contains carbon and can be thermally decomposed to the graphitization catalyst. A polar or nonpolar organic substance having a boiling point of 60 to 400 ° C. Solvents may be used. As such an organic solvent, an alcoholic organic solvent, an etheric organic solvent, a ketone organic solvent, an ester organic solvent, an organic acid organic solvent, or the like can be used. The organic solvent can be easily adsorbed with a graphitized metal catalyst, has good reactivity, and has a reducing power. It is more preferable to use an alcohol type and an ether type organic solvent from the point of excellence. As such alcohol-based organic solvents, monohydric alcohols and polyhydric alcohols may be used alone or in combination. Promonol, pentanol, hexanol, heptanol, octanol and the like may be used as the monohydric alcohol. Examples of the polyhydric alcohols include propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, octylene glycol, tetraethylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 1,4- Butanediol, 2,3-butanediol, dimethyl-2,2-butanediol-1,2 and dimethyl-2,2-butanediol-1,3 and the like can be used. The monohydric alcohols and polyhydric alcohols may include ether groups in addition to hydroxy groups.

When the liquid carbonaceous material is used, carburization may be performed by a preliminary heat treatment process, and the liquid carbonaceous material is pyrolyzed by a graphitization catalyst. The process of thermally decomposing liquid carbonaceous material by the graphitization catalyst is already known (Nature, vol 418, page 964) and the like, for example, the thermal decomposition products of organic solvents such as polyhydric alcohols are alkanes, H ₂ , CO ₂ , H ₂ O and the like, and the carbon component in the decomposition product is carburized inside the catalyst. This document is incorporated herein by reference.

The preliminary heat treatment process for such pyrolysis may be performed for 10 minutes to 24 hours at a temperature of 100 to 400 ℃.

On the other hand, by controlling the degree of carburization in the carburizing process as described above, it is possible to control the carbon content in the catalyst, thereby making it possible to control the thickness of the graphene layer formed in the subsequent graphene production process to a single layer. For example, in the decomposition reaction process of the liquid carbonaceous material, when a material that is easily decomposed is used, the content of decomposed carbon increases, and as a result, a large amount of carbon can be carburized in the catalyst. In addition, by controlling the carburization process by adjusting the heat treatment temperature and time, it is possible to control the content of carbon carburized in the catalyst, thereby controlling the degree of graphene production. Thus, the thickness of the graphene layer can be easily controlled in a single layer.

As described above, after the carbon-containing polymer or the liquid carbon-based material is contacted with the graphitized catalyst metal film, heat treatment is performed to form graphene on the catalyst metal film. Such a heat treatment process can be carried out in the same manner as the gas phase method described above.

-Graphene Formation Process (SiC Growth Method)

Graphene can be formed directly on the substrate without a separate carbon source. As such a substrate, for example, a SiC wafer can be used. Graphene grows epitaxially on SiC wafers, and graphene can grow on both the silicon and carbon surfaces of SiC wafers. It is possible to grow graphene with better uniformity on the silicon surface than on the carbon surface of the SiC wafer.

An SiC layer, which is an example of the substrate, may have a thickness of about 1 nm to about 500 μm. Within this range it is possible to supply sufficient carbon for graphene growth. This may be heat treated to form a graphene structure.

When a carbon-containing substrate, for example, a SiC wafer, is used as the substrate, a separate carbon supply source is not required because the wafer itself becomes a carbon supply source. In this case, the internal Si-C bond is weakened by heat treatment, and carbon is dissociated to the surface to be released. Then, they bond with each other to form graphene.

Heat treatment conditions for forming the graphene may be performed for about 1 minute to about 2 hours at a temperature of about 1,000 ^o C to about 2,000 ^o C in a vacuum or inert atmosphere.

The inert atmosphere means that the container is filled with an inert element such as argon or helium, and the pressure may be in the range of about 100 torr to about 700 torr.

The single layer graphene obtained by various methods as described above may have an area of 1 cm ² or more, and the graphene having fewer defects may be obtained, and thus the single layer graphene may have 10 or less wrinkles per unit area of 1000 μm ² . Can be. In addition, these monolayer graphene may be present in a range of 99% or more per unit area of 1 mm ² .

The semiconducting graphenes obtained by containing alkali metals on the monolayer graphene thus prepared are various electric devices, for example, sensors, bipolar junction transistors, field effect transistors, heterojunction bipolar transistors, single electron transistors, A light emitting diode, an organic light emitting diode, etc. can be illustrated.

Among these, an example of the field effect transistor is shown in FIG. In FIG. 2, a silica substrate 12 is present on the substrate 11, on which the semiconductorized, alkali metal containing monolayer graphene 13 is placed. Source electrodes 14 and drain electrodes 17 exist on left and right sides, and gate electrodes 15 exist with insulator layer 16 therebetween. Here, the current flowing between the source and drain electrodes is controlled by applying a voltage to the gate electrode. That is, the semiconductor layer forms a channel region, and the current flowing between the source electrode and the drain electrode is controlled by a voltage applied to the gate electrode, thereby operating on / off.

Here, the distance between the source electrode and the drain electrode is determined according to the use of the thin film transistor, and is, for example, 0.1 to 1 mm, for example, 1 to 100 m, or 5 to 100 m.

The material of the insulator layer in the transistor according to one embodiment is not particularly limited as long as it has electrical insulation properties and can be formed as a thin film. Metal oxides (including silicon oxides) and metal nitrides (silicon nitrides) And a material having an electrical resistivity of 10 OMEGA cm or more at room temperature, such as a polymer and an organic low molecule, can be used. For example, an inorganic oxide film having a high dielectric constant can be used.

The inorganic oxide may be silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium titanate zirconate, lead titanate zirconate, lead lanthanum titanate, strontium titanate, Barium titanate, barium magnesium fluoride, lanthanum oxide, fluorine oxide, magnesium oxide, bismuth oxide, bismuth titanate, niobium oxide, strontium bismuth titanate, strontium bismuth tantalate, bismuth pentoxide, bismuth niobate tantalum, bismuth trioxide And combinations thereof. Examples thereof include silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide.

In addition, inorganic nitrides such as silicon nitride (Si ₃ N ₄ , Si _x N _y (x, y > 0)) and aluminum nitride can also be suitably used.

Further, the insulator layer may be formed of a precursor containing an alkoxide metal, and the insulator layer is formed by coating a solution of the precursor, for example, on a substrate, and subjecting it to a chemical solution including heat treatment.

As a metal in the said alkoxide metal, it selects from a transition metal, a lanthanoid, or a main group element, for example, Barium (Ba), strontium (Sr), titanium (Ti), bismuth (Bi), tantalum Rum (Ta), zirconium (Zr), iron (Fe), nickel (Ni), manganese (Mn), lead (Pb), lanthanum (La), lithium (Li), sodium (Na), potassium (K), Rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), niobium (Nb), thallium (Tl), mercury (Hg), copper (Cu), Cobalt (Co), rhodium (Rh), scandium (Sc), yttrium (Y), etc. are mentioned. As the alkoxide in the alkoxide metal, for example, alcohols containing methanol, ethanol, propanol, isopropanol, butanol, isobutanol and the like, methoxy ethanol, ethoxy ethanol, propoxy ethanol, butoxy And alkoxy alcohols containing ethanol, pentoxy ethanol, heptoxy ethanol, methoxy propanol, ethoxy propanol, propoxy propanol, butoxy propanol, pentoxy propanol, heptoxy propanol and the like.

When the insulator layer according to one embodiment is made of the above materials, polarization easily occurs in the insulator layer, and the threshold voltage of the transistor operation can be reduced. In addition, when the insulator layer is formed of silicon nitride such as Si ₃ N ₄ , Si _x N _y , and SiON _x (x, y> 0), the depletion layer is more likely to be generated, and the threshold of the transistor operation is achieved. The voltage can be further reduced.

Examples of the insulator layer using the organic compound include polyimide, polyamide, polyester, polyacrylate, photoradical polymerization system, photocurable resin of photocationic polymerization system, copolymer containing acrylonitrile component, polyvinylphenol, Polyvinyl alcohol, a novolak resin, cyanoethyl pullulan, etc. can also be used.

In addition, wax, polyethylene, polychloropyrene, polyethylene terephthalate, polyoxymethylene, polyvinyl chloride, polyvinylidene fluoride, polymethyl methacrylate, polysulfone, polycarbonate, polyimide cyanoethyl pullulan, poly (Vinylphenol) (PVP), poly (methyl methacrylate) (PMMA), polycarbonate (PC), polystyrene (PS), polyolefin, polyacrylamide, poly (acrylic acid), novolac resin, resol resin, polyimide In addition to polyxylene and epoxy resins, it is also possible to use a polymer material having a high dielectric constant such as pullulan.

The insulator layer may be a mixed layer using a plurality of inorganic or organic compound materials as described above, or may be a laminate structure thereof. In this case, the performance of the device may be controlled by mixing or laminating a material having a high dielectric constant and a material having water repellency as necessary.

As the method for forming the insulator layer, a dry process such as vacuum deposition, molecular beam epitaxial growth, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, atmospheric plasma, or spray coating or spin coating Wet processes such as a coating method, a blade coating method, a dip coating method, a casting method, a roll coating method, a bar coating method, a die coating method and the like, a printing or inkjet patterning method, and the like. Can be used depending on the material. The wet process is a method of applying and drying a liquid obtained by dispersing an inorganic oxide fine particle in an arbitrary organic solvent or water using a dispersing aid such as a surfactant as necessary, or applying and drying a solution of an oxide precursor such as an alkoxide body. The so-called sol-gel method is used.

A metal atomic layer and / or a metal ion layer may be further formed between the graphene layer, which is the semiconductor layer, and the insulator layer. The metal atomic layer may include Zn, Al, Ga, Zr, Ni, Co, Pd, or a mixture thereof. The metal ion layer may comprise ions of Zn, Al, Ga, Zr, Ni, Co, Pd or mixtures thereof, which may be present in the form of metal salts. As the corresponding anion of the metal salt may be exemplified _{^{halogen, (COOH) -1, NO 3}} 2-, SO 4 2-, CO 3 -2. These metal atom layers or metal ion layers may have a thickness in which metal atoms or metal ions are laminated in one to three layers.

The metal atomic layer or metal ion layer may be formed by a method known in the art, for example, vacuum deposition, molecular beam epitaxial growth, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method Dry process such as atmospheric plasma method, spray coating method, spin coating method, blade coating method, dip coating method, casting method, roll coating method, bar coating method, die coating method, etc. Wet processes, such as a method by patterning, such as a jet, can be mentioned, It can use according to a material, It does not specifically limit.

The substrate in the transistor, for example, a thin film transistor, serves to support the structure of the thin film transistor, and as a material, inorganic compounds such as metal oxides and nitrides, plastic films (PET, PES, PC), It is also possible to use a metal substrate or a composite or a laminate thereof. In addition, when the structure of a thin film transistor can fully be supported by components other than a board | substrate, it is also possible not to use a board | substrate. In addition, as a material of a substrate, a silicon (Si) wafer is often used. In this case, Si itself can be used as the gate electrode and the substrate. It is also possible to oxidize the surface of Si to form SiO ₂ and to utilize it as an insulating layer. In this case, metal layers, such as Au, are formed into a film as a lead wire connection electrode on the Si substrate of a board | substrate and a gate electrode.

The material of the gate electrode, the source electrode and the drain electrode in the transistor according to one embodiment is not particularly limited as long as it is a conductive material. Platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, Indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide antimony, indium tin oxide (ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, Silver pastes and carbon pastes, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloys, magnesium, lithium, aluminum, magnesium / copper mixtures, magnesium / Silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide mixtures, lithium / aluminum mixtures, and the like, An electrode can be formed by forming into a film by the vapor deposition method or the vacuum vapor deposition method.

In the transistor according to one embodiment, as the source electrode and the drain electrode, one formed by using a fluid electrode material such as a solution, paste, ink, and dispersion liquid containing the conductive material may be used. As a dispersion containing metal microparticles | fine-particles, a well-known electrically conductive paste etc. can also be used, for example, It is preferable if it is a dispersion containing metal microparticles | fine-particles of 0.5 nm-50 nm and 1 nm-10 nm normally. Examples of the metal fine particles include platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, and mol. Ribdenum, tungsten, zinc and the like can be used.

It is preferable to form an electrode using the dispersion which disperse | distributed these metal microparticles | fine-particles mainly using the dispersion stabilizer which consists of organic materials in water and the dispersion medium which is arbitrary organic solvents. As a method for producing a dispersion of the metal fine particles, a physical production method such as evaporation in a gas, a sputtering method, or a metal vapor synthesis method, or a chemical production method of producing metal fine particles by reducing metal ions in a liquid phase such as a colloid method or a coprecipitation method For example.

The electrode is molded using these metal fine particle dispersions, and the solvent is dried. Then, the metal fine particles are thermally fused by heating in a shape in a range of 100 ° C to 300 ° C, for example, 150 ° C to 200 ° C, if necessary. An electrode pattern having a desired shape can be formed.

Moreover, as a material of a gate electrode, a source electrode, and a drain electrode, the well-known conductive polymer which improved conductivity by doping etc. can be used, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene (polyethylene dioxythiophene and polystyrene sulfonate) Complexes of phonic acid), and complexes of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid are also suitably used. These materials can reduce the contact resistance between the semiconductor layer of the source electrode and the drain electrode.

It is preferable that the material which forms a source electrode and a drain electrode is small in electrical resistance in the contact surface with a semiconductor layer among the above-mentioned examples. The electrical resistance at this time corresponds to the field effect mobility when the current control device is manufactured, and in order to obtain large mobility, it is necessary that the resistance is as small as possible.

The electrode is formed by, for example, vapor deposition, electron beam deposition, sputtering, atmospheric plasma method, ion plating, chemical vapor deposition, electrodeposition, electroless plating, spin coating, printing or ink jet. Moreover, as a method of patterning as needed, the method of electrode formation of the electroconductive thin film formed using the said method using the well-known photolithographic method or the lift-off method, and thermal transfer on metal foils, such as aluminum and copper, , Ink jet, or the like, is a method of forming and etching a resist. Moreover, the solution or dispersion liquid of a conductive polymer, the dispersion liquid containing metal microparticles | fine-particles, etc. can also be patterned directly by the inkjet method, and can also be formed from a coating film by lithography, laser polishing, etc. Moreover, the method of patterning the conductive ink, conductive paste, etc. containing a conductive polymer, metal fine particles, etc. by printing methods, such as a convex plate, a recessed plate, a flat plate, and screen printing, can also be used.

The film thickness of the electrode thus formed is not particularly limited as long as the current passes, but is, for example, in the range of 0.2 nm to 10 μm or 4 nm to 300 nm. If it is in this range, as a film thickness becomes thin, resistance becomes high and a voltage drop does not generate | occur | produce.

In the transistor according to the embodiment, for example, a buffer layer may be provided between the semiconductor layer, the source electrode, and the drain electrode for the purpose of improving the implantation efficiency. As the buffer layer, a compound having an alkali metal or alkaline earth metal ion bond such as LiF, Li ₂ O, CsF, NaCO ₃ , KCl, MgF ₂ , CaCO _3, etc., used for the cathode of the organic EL device may be used as the buffer layer. Can be. Moreover, the compound used as an electron injection layer and an electron carrying layer can also be inserted in organic electroluminescent element, such as Alq (tris (8-quinolinol) aluminum complex).

The buffer layer has the effect of lowering the threshold voltage by driving the carrier injection barrier and driving the transistor at low voltage. The buffer layer may be thin between the electrode and the semiconductor layer, and the thickness thereof is 0.1 nm to 30 nm, or 0.3 nm to 20 nm.

In the thin film transistor, the light emitting device may be electrically connected to the thin film transistor, and then the light emitting device may be controlled using a current flowing between a source and a drain, and the flat panel display may be configured using the thin film transistor. .

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Preparation Example 1 Preparation of Graphene Monolayer

The 2-inch SiC wafer was placed in a chamber filled with 680 torr of argon gas and heated at a temperature of 1,650 ° C. for 10 minutes. It was then slowly cooled to form an epitaxial graphene monolayer structure having a size of 1 mm × 10 mm.

The light transmittance of the graphene monolayer obtained above was measured using the absorption of light having a wavelength of 450 nm to 700 nm. 3 shows the light transmission of the graphene monolayer. As can be seen in Figure 3, the light transmittance of the graphene monolayer showed a value of about 97% to about 98%. This shows that the graphene monolayer was formed in the above process.

Preparation Example 2 Preparation of Graphene Monolayer

Cu foil (Wacopa Co., ltd) having a thickness of 75 μm was placed in the chamber. The Cu foil was then heated at 1,000 ° C. for 30 minutes using a halogen lamp while adding hydrogen gas to the chamber at 200 sccm (standard cubic centimeters per minute). And a mixed gas of CH ₄ 20sccm / H ₂ 4sccm was added to the chamber for 30 minutes. The chamber was then slowly cooled to grow uniformly oriented with graphene to form a 10 mm × 10 mm sized graphene monolayer with a thickness of one layer.

A chlorobenzene solution (5% by weight) in which poly (methylmethacrylate) ("PMMA") was dissolved was then applied onto the substrate on which the graphene monolayer was formed at a rate of 1,000 revolutions per minute (60 rpm) for 60 seconds. It was. The resulting product was immersed in an etchant (CE-100, Transene Co., Ltd.) for 1 hour to remove Cu foil to separate the graphene monolayer bound to PMMA. A graphene monolayer bonded to the PMMA was placed on a silica / silicon substrate, dried and then PMMA was removed using acetone to obtain a graphene monolayer.

In the silica / silicon substrate, the silica (SiO ₂ ) substrate has a size of 1 cm × 1 cm and a thickness of 300 μm, and is placed on a silicon substrate having a size of 1 cm × 1 cm and a thickness of 500 μm.

Example 1

As obtained in Preparation Example 1, a graphene monolayer having a size of 1 mm × 10 mm was placed on the SiC substrate.

Sodium (Na) was then formed on the monolayer graphene at a thickness of 10 mm 3 using a sputtering equipment.

4 to 7 show a process in which sodium is gradually formed in the monolayer graphene. FIG. 4 shows that sodium is initially formed as an epitaxial structure on graphene, FIG. 5 shows the growth of sodium to form nanoclusters, FIG. 6 shows sodium to form nanorods, and FIG. Finally, the sodium of the two-dimensional thin film structure is formed.

FIG. 8 shows the results of bandgap measurement using an optical transmittance measurement method for a single-layer graphene having sodium in the two-dimensional thin film structure. As shown in FIG. 8, it can be seen that a bandgap of about 0.8 eV is formed.

Example 2

As obtained in Preparation Example 2, the silica (SiO ₂ ) substrate has a size of 1 cm X 1 cm and a thickness of 300 μm, is located on a silicon substrate having a size of 1 cm X 1 cm and a thickness of 500 μm, and 1 mm X A graphene monolayer having a size of 10 mm was placed on the silica substrate.

Sodium (Na) was formed on the monolayer graphene at a thickness of 10 mm 3 using a sputtering equipment.

Claims (18)

Single layer graphene containing alkali metals. The method of claim 1,
Single layer graphene is the alkali metal is one or more selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr). The method of claim 1,
Single layer graphene wherein the alkali metal is sodium (Na). The method of claim 1,
Wherein said alkali metal is present on at least one surface of said monolayer graphene. The method of claim 1,
Single layer graphene wherein the alkali metal has a two-dimensional thin film structure. The method of claim 1,
Single layer graphene wherein the alkali metal is in the form of a thin film, nanorods and / or nanoclusters. The method of claim 1,
Wherein said alkali metal is about 30 to about 99% of the total surface area of said monolayer graphene. The method of claim 1,
Wherein said alkali metal is about 50 to about 90% of the total surface area of said monolayer graphene. The method of claim 1,
Wherein said monolayer graphene has a bandgap of about 0.4 eV or greater. The method of claim 1,
Wherein said monolayer graphene has a bandgap of about 0.45 eV to about 0.8 eV. The method of claim 1,
Wherein said monolayer graphene has a bandgap of about 0.6 eV to about 0.8 eV. The method of claim 1,
The single layer graphene is a single layer graphene having an area of 1 cm ² or more. The method of claim 1,
The single layer graphene is a single layer graphene having a wrinkle less than 10 per unit area 1000㎛ ² . The method of claim 1,
The monolayer graphene is present in the range of 99% or more per 1 mm ² unit area graphene. The method of claim 1,
Single layer graphene will be further provided with a substrate under the single layer graphene. 16. The method of claim 15,
The substrate is a plastic substrate, Si substrate, glass substrate, GaN substrate, silica substrate, Ni substrate, Co substrate, Fe substrate, Pt substrate, Pd substrate, Au substrate, Al substrate, Cr substrate, Cu substrate, Mn substrate, Mo substrate And a substrate comprising at least one of a Rh substrate, an Ir substrate, a Ta substrate, a Ti substrate, a W substrate, a U substrate, a V substrate, and a Zr substrate. An electric device comprising the single layer graphene of claim 1. The method of claim 17,
The electric device is a sensor, a bipolar junction transistor, a field effect transistor, a heterojunction bipolar transistor, a single electron transistor, a light emitting diode, or an organic light emitting diode.

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